[DaveInHull]

Hi, I'm very new to CNC machining and have got a Chinese 6040 machine which I've had some success with acrylic and wood.
I've now moved on to aluminium and am trying to cut just a simple shape involving milling a square piece to have rounded corners and a whole in the middle. I'm using Fushion360 to do the design and produce the g-code.
I'm using 6mm 4 flute HSS flat end bit.
The corners and other simple menouvers work ok, but the whole in the centre causes the machine to judder and eventually miss steps, particularly in the early stages of cutting it at each layer.
The g-code starts with a fairly rapid small circular movement as it enters the material and then spirals outwards to the required diameter, which is when it starts struggling.
The spindle speed is 10000 which was set by Fushion360 for aluminium.
I know there are probably many factors and parameters involved which would make it difficult to give me a specific answer, but has anyone got any ideas on where I should be looking?
Thanks in advance
Dave

[bostosh]

Re-post without the spiral, the controller is going nuts calculating the end positions of multiple circular interpolations..

[DaveInHull]

Many thanks bostosh, will have to look at Fusion360 to see how I can tell it to stop the spiralling ....